The present invention relates to non-magnetic stainless steel having excellent workability, and particularly to non-magnetic stainless steel which permits an increase in the life of a mold used in machine working and an improvement in the quality of the precision parts produced by working.
Many small precision parts such as non-magnetic gears and the like are mounted in domestic electrical equipment such as television and video tape recorder (VTR), computers, magnetic recording devices, electronic equipment and the like. For example, small oval-shaped beam guide parts, each of which has a length of 15 mm, a width of 5 mm and a thickness of 2 mm and which are laminated in multiple stages, are mounted in an electron gun used for color television cathode ray tubes (CRT).
Such electron guns are generally used for attracting or repulsing the thermions emitted from the cathode of an electrode heated by a heater, converging them to a narrow beam or diffusing them to a wide beam when the thermions are passed through beam guide parts so as to apply them to a predetermined fluorescent surface of a cathode ray tube and to emit light. Each of color television cathode ray tubes is equipped with three electron guns for the primary colors, i.e., red, blue and green, and three through holes are formed in parallel in each of the beam guide parts in the axial direction thereof. Each of the beam guide parts is made of a non-magnetic material for the purpose of preventing any disturbance of an electron beam from being produced by magnetization with the passage of time.
Conventional beam guide parts are formed by, for example, blanking out them from a plate of 18-8 stainless steel which consists of an alloy containing 8.0 to 8.3 wt % of Ni, 18 to 19 wt % of Cr, 0.05 to 0.08 wt % of C, 0.8 to 1.0 wt % of Si and 1.0 to 1.4 wt % of Mn and then forming the three through holes by punching the plate.
When small beam guide parts used for television sets are produced by blanking out from 18-8 stainless steel, which is a general material, however, since the mold or the pressing part of a pressing system is easily damaged or broken off, the part products are damaged or broken. There is thus a problem in that the quality of the products is deteriorated, and the yield of the products is significantly decreased.
In the conventional blanking process, the operator must conduct a troublesome work of constantly checking the occurrence of defective products. In a stage where defective products easily occur, the operation is stopped, and the mold is polished again.
There are thus disadvantages in that, since the substantial life of the mold is short, the operation cannot be continued for a long period, and the production efficiency is low, and in that the maintenance, control and checking works require a great deal of labor.
In particular, when beam guide parts for television sets are produced by using conventional materials, the materials have poor blanking quality and a tendency to be greatly deformed. It is therefore necessary for preventing the deformation to increase the distance between the through holes formed in each part body.
Since the diameter of each of the through holes is thus relatively decreased, it is difficult to focus the electron rays passing through the through holes and increase the luminance of a cathode ray tube.